A packet or datagram is a piece of a message transmitted over a packet-switching network. An example of a packet-switching network is the Internet where enormous quantities of data are communicated between various network points. In the Internet environment, content to be communicated between two endpoints is broken up into packets and these packets may follow different paths whilst travelling between the endpoints. It will be appreciated that the content of packets may be ordinary or anomalous.
An example of anomalous content in a packet is data that repeats with high frequency, such as the data associated with viruses, computer worms, or the like. In these circumstances, it may be advantageous to identify anomalous content in packets and then monitor subsequent packets for the anomalous content. Anomalous content in a packet may be identified by a “signature” or sequence of bytes that is present in the content. Then, all subsequent packets are checked to see if the signature is present and, if so, appropriate action may be taken to reduce any negative effects of the anomalous packet on the network.